Linux: update protoc wrapper to allow building with system protobuf.

build/protoc.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file is meant to be included into a target to provide a rule
 # to invoke protoc in a consistent manner. For Java-targets, see
 # protoc_java.gypi.
 #
 # To use this, create a gyp target with the following form:
 # {
@@ skipping 64 matching lines @@
         '<(cc_dir)/<(RULE_INPUT_ROOT).pb.cc',
         '<(cc_dir)/<(RULE_INPUT_ROOT).pb.h',
       ],
       'action': [
         'python',
         '<(protoc_wrapper)',
         '--include',
         '<(cc_include)',
         '--protobuf',
         '<(cc_dir)/<(RULE_INPUT_ROOT).pb.h',
+        # Using the --arg val form (instead of --arg=val) allows gyp's msvs rule
+        # generation to correct 'val' which is a path.
+        '--proto-in-dir','<(proto_in_dir)',
+        # Naively you'd use <(RULE_INPUT_PATH) here, but protoc requires
+        # --proto_path is a strict prefix of the path given as an argument.
+        '--proto-in-file','<(RULE_INPUT_ROOT)<(RULE_INPUT_EXT)',
+        '--use-system-protobuf=<(use_system_protobuf)',
         '--',
         '<(protoc)',
-        # Using the --arg val form (instead of --arg=val) allows gyp's msvs rule
-        # generation to correct 'val' which is a path.
-        '--proto_path','<(proto_in_dir)',
-        # Naively you'd use <(RULE_INPUT_PATH) here, but protoc requires
-        # --proto_path is a strict prefix of the path given as an argument.
-        '<(proto_in_dir)/<(RULE_INPUT_ROOT)<(RULE_INPUT_EXT)',
         '--cpp_out', '<(cc_generator_options)<(cc_dir)',
         '--python_out', '<(py_dir)',
       ],
       'msvs_cygwin_shell': 0,
       'message': 'Generating C++ and Python code from <(RULE_INPUT_PATH)',
       'process_outputs_as_sources': 1,
     },
   ],
   'dependencies': [
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protoc#host',
@@ skipping 11 matching lines @@
   },
   'export_dependent_settings': [
     # The generated headers reference headers within protobuf_lite,
     # so dependencies must be able to find those headers too.
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
   ],
   # This target exports a hard dependency because it generates header
   # files.
   'hard_dependency': 1,
 }